The airducts seemed to work really well, and within 20 minutes we had a raging fire. Covering over the The Pit with tin, I left the airducts open, and allowed it to vent through the gap in the tin sheeting.

After 8 hours we opened it to have a look

the fotos for this are terrible and show nothing but a black hole and smoke. so you don't get to see them.The wood wasn't fully burnt, but there was a significant charcoal cunks in there. we covered it over again to head back the following eve.